Water supply for hydropower is at worryingly low levels in Canada and the United States, as climate change raises temperatures and alters precipitation patterns, threatening clean energy plans.

Overall, Canada generated 3.9% less electricity in 2023 than the year before—the lowest in years, even though additional generating power comes online each year, Statistics Canada reported last month. “Nearly all of the decline in electricity generation in 2023 was weather-related.”

With three-fifths of the country’s electricity produced at hydroelectric stations, hydro was the largest contributor to the national decline in electricity generation in 2023, amid “the hottest summer on record since 1940” and unusually low precipitation in Western and Central Canada, StatsCan added.

Of particular note, Manitoba, British Columbia, and Quebec—which rely on hydropower for nearly all their electricity needs—each struggled with differing challenges of drought, heat, and low spring runoff. The provinces had to use more fossil fuels, import power, or—in the case of Quebec—cut down electricity exports.

Similar trends are emerging south of the border in the western U.S., where last year hydropower generation dropped 11% to its lowest level in 22 years. The decline followed modest precipitation levels in the year before and a spring heatwave that melted snowpack rapidly enough to exhaust the water supply needed for generation in the summer, said the U.S. Energy Information Administration (EIA).

The states with the biggest decline included Washington and Oregon, which each produced more than 20% less energy than in 2022. California, however, balanced that loss after atmospheric rivers drenched the state and nearly doubled hydropower generation compared to the year before. Looking ahead, the EIA anticipates that hydropower production in the western states will fall another 12% in 2024.

Hydropower is seen as an important renewable energy source in the energy transition—even though it comes with its own environmental problems, is expensive to build, and can dispossess communities of their lands.

For Canadian and U.S. electricity planners focused more narrowly on carbon metrics, the declining trend in hydropower generation could also disrupt plans to use it to meet emission targets. Hydro-Québec’s recent net-zero plan, for instance, involves developing 3,800 to 4,200 megawatts of new hydroelectric generation—amid a drier climate. And globally, the International Energy Agency calls for increasing hydropower capacity by 40% to reach net-zero by 2050.

“Given the scale of the challenge presented by emissions reduction and the fact that existing non-emitting sources like hydro may become less abundant, society must recognize that there will be less energy available in the future,” veteran energy analyst David Hughes told The Tyee.